1. Technical Field
The present disclosure relates to display technology, and particularly to a display driving unit providing decreased flicker of a liquid crystal display (LCD) and a method for using the same.
2. Description of Related Art
Hold-type display technology is widely used in LCD applications. Referring to FIG. 11, an LCD stores a γ curve γ2.2, which describes the functional relationship between the gray level of images displayed by the LCD and the luminance of each pixel of the LCD. When the LCD displays images, it regulates the luminance of each pixel thereof according to the gray level of the images corresponding to the pixel and γ2.2. For example, also referring to FIG. 12, a pixel of the LCD is used to respectively display its corresponding portions of a plurality of sequential images on a plurality of sequential display periods for example, T0-T1, T1-T2, T2-T3. On each display period, the luminance of the pixel is sequentially regulated according to the gray level of the images and γ2.2. However, commonly used hold-type display technology may generate blur. When the displayed images are changed for example, on T1/T2, each previous image is directly replaced by the subsequent image. If the luminance of some pixels is not regulated in a timely manner according to the gray level of the next image, the portions of the previous image corresponding to these pixels may temporarily remain and overlap the next image, generating blur.
Black insertion technology is widely used to overcome the above-detailed shortcoming. Also referring to FIG. 13, when an LCD sequentially displays a plurality of common images, the common images are respectively displayed on separate display periods for example, T0-T01, T1-T11, T2-T21. Any two adjacent display periods are separated by a black insertion period for example, T01-T1, T11-T2, T21-T3, and the LCD displays a complete black image in no luminance on each black insertion period. Each complete black image can prevent the previous common image from overlapping the subsequent common image, thereby preventing blur. However, since the complete black images have no luminance, they may decrease the average luminance of the LCD. Furthermore, the complete black images contrast clearly with other images. When the complete black images and the common images are alternately displayed by the LCD, the LCD may generate flicker.
Gray insertion technology is widely used to overcome the detailed shortcoming of black insertion technology. Also referring to FIG. 14, an LCD stores a first γ curve γ1 for describing the functional relationship between the gray level of common images displayed by the LCD and the luminance of each pixel of the LCD, and a second γ curve γ2 for describing the functional relationship between the gray level of gray insertion images displayed by the LCD and the luminance of each pixel of the LCD. The average of the luminance respectively determined according to γ1 and γ2 is set to approximately equivalent to the luminance determined according to the γ curve γ2.2, such that the average luminance of the LCD using gray insertion technology is similar to that of LCDs not using the gray insertion technology, thereby saving electric power and improving display quality. The first γ curve γ1 is above the γ curve γ2.2, and the second γ curve γ2 is below the γ curve γ2.2. Other than the luminance corresponding to the lowest gray level, that is the luminance of a complete white image, and the highest gray level, that is the luminance of a complete black image, of the LCD, the luminance corresponding to any gray level according to γ1 is higher than the luminance corresponding to any gray level according to γ2.2, and the luminance corresponding to any gray level according to γ2 is lower than the luminance corresponding to any gray level according to γ2.2.
Also referring to FIG. 15, when the LCD sequentially displays a plurality of images, each image is displayed in a display period for example, T0-T1, T1-T2, T2-T3. Each display period includes a previous common display sub-period for example, T0-T01, T1-T11, T2-T21, and a sequent gray insertion sub-period for example, T01-T1, T11-T2, T21-T3. In the common display sub-period, the luminance of each pixel of the LCD is regulated according to the gray level of the image and γ1, and thus the image is normally displayed in higher luminance, that is, displaying a common image. In the gray insertion sub-period, the luminance of each pixel of the LCD is regulated according to the gray level of the image and γ2, and thus the image is displayed in lower luminance, that is, as a gray insertion image. Until the common display sub-period of the subsequent display period comes, the gray insertion image is replaced by the subsequent common image. In this way, any two common images in higher luminance regulated according to γ1 are separated by a gray insertion image in lower luminance regulated according to γ2. Each gray insertion image can prevent the previous common image from overlapping the subsequent common image, thereby preventing blur. Furthermore, the gray insertion images contrast with the common images less clearly than complete black images. Compared with use of black insertion technology, an LCD using the gray insertion technology exhibits decreased flicker and enhanced average luminance.
However, in the gray insertion technology described, γ1 and γ2 are respectively positioned above and below γ2.2. In many gray levels, the luminance corresponding to a gray level according to γ1 may be higher than the luminance corresponding to the same gray level according to γ2. Thus, the common images (in higher luminance regulated according to γ1) may still contrast clearly with the gray insertion images (in lower luminance regulated according to γ2) and the gray insertion technology only refers to one γ curve in one sub-period. Despite improving on black insertion technology, the gray insertion technology may still generate flicker.
Therefore, there is room for improvement within the art.